Shakespeare's Characters: Feste (Twelfth Night)

From The Works of William Shakespeare. Vol. 16. Ed. Evangeline Maria O'Connor. J.D. Morris and Co.

The Clown in this play, who, I am inclined to think, should bear his name all through by as good a right as Touchstone, is a remarkable creation, and very essential to the knitting and coherence of the general play. His musical talent is most diversified; he gives as readily and with equal effect the tender love song suited to the dreamy and poetical being of the Duke, or the noisy catch that shakes the rafters and calls up Malvolio at
midnight. Thus catholic in his artistic range, he has a
not less wide intellectual scope. He plumbs the depth
accurately of his mistress's exhausted sorrow, penetrates
the destiny of Maria and Sir Toby's weak pia mater,
holds up a mirror to the opalescent humours of the
Duke, and takes remarkably good care of his own economical resources, by asking on every occasion when he is safe to obtain — yet free from slyness withal, genial and enjoyable, as he is free of speech. Still, apart from a certain degree of loyalty to his mistress, he knows the world too well — this it is to be wise and to suffer for it, to remain very long in society of the same tone, or to feel much sympathy for anybody, or consequently to get much in return. With no great interest in the practical
jests and bear-baitings that are rife around him, he does
not refuse, however, to gratify his pique of profession,
by lending a helping hand in duping the churlish steward.
Lloyd: Critical Essays on the Plays of Shakespeare.

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Of all Shakespeare's clowns, he is the best endowed with a many-sided mirth, as indeed he should be to pass lightly through the mingled romance and roystering of the play and favor all its moods. The sentiment of the Duke is as inebriated as the revelling which Malvolio rebukes.
Olivia's protracted grief for her brother is carefully cosseted by her, as if on purpose to give the Clown an opportunity.

Clo. Good madonna, why mournest thou?Oliv. Good fool, for my brother's death.Clo. I think his soul is in hell, madonna. Oliv. I know his soul is in heaven, fool. Clo. The more fool, madonna, to mourn for your brother's soul being in heaven. — Take away the fool, gentlemen.

All the characters, noble and common, have some
weakness which he intuitively rallies. The charm of the
comedy lies in these unsubstantial moods of the chief
personages which consort with the more substantial
whims and appetites of the others. The only sobriety
is vested in the Clown; for all his freaks have a consistent disposition. So the lovely poetry of the mock mourners alternates with the tipsy prose of the genuine fleshly fellows. Their hearty caterwauling penetrates to Olivia's fond seclusion, and breaks up her brooding.

Feste is everywhere at home. When he plays the
curate's part, Malvolio beseechingly cries, "Sir Topas,
Sir Topas!" The Clown says aside, "Nay, I am for all
waters" — that is, for topaz, diamond, gems of the first
water, all many-colored facets, I'll reflect. And he does
so in this conversation which he holds with Malvolio,
who says, "I am no more mad than you are; make the trial of it in any constant question." Then Feste airs his learning: "What is the opinion of Pythagoras concerning wild-fowl?" and makes his question lead up to a sharp retort, when Malvolio answers, "That the soul of our grandam might haply inhabit a bird"; for then Feste
says, "Thou shalt hold the opinion of Pythagoras ere I
will allow of thy wits, and fear to kill a woodcock lest thou
dispossess the soul of thy grandam." For it was a
country notion that the woodcock was the foolishest of
birds; so he translates Malvolio's grandam into one, and
leaves him to inherit her absence of wits. And Malvolio
was so devoured by mortification and anxiety that he does not notice when Feste cannot restrain his burlesquing knack, but makes the pretended curate say that Malvolio's cell "hath bay-windows, transparent as barricadoes, and the clearstores toward the south-north are as lustrous as ebony."
Weiss: Wit, Humor, and Shakespeare.